Silicon heterojunction solar cell passivation in combination with nanocrystalline silicon oxide emitters

Silicon heterojunction solar cells (SHJ) are well known for their high efficiencies, enabled by their remarkably high open-circuit voltages (V_OC). A key factor in achieving these values is a good passivation of the crystalline wafer interface. One of the restrictions during SHJ solar cell production is the limitation to comparably low post processing temperatures due to the deteriorating effect of high temperatures on the passivation properties of passivating intrinsic amorphous silicon (a-Si:H(i)) layers combined with conventional boron-doped amorphous silicon (a-Si:H(p)) emitter layers. We present a boron-doped nanocrystalline silicon oxide (nc-SiO_x:H(p)) material that exhibits superior annealing behaviour. Passivation stacks consisting of a-Si:H(i) and nc-SiO_x:H(p) emitter layers show an increase in minority carrier lifetime with post deposition annealing temperatures ≤293°C. To our knowledge, there have been no earlier reports showing that annealing of complete passivation stacks including p-type silicon-based layer at such high temperatures is beneficial.